To save electricity, it is generally needed to be switched between main lighting realized by fluorescent lamps and weak lighting realized by LEDs. However, to switch between main lighting and weak lighting, a fluorescent lamp driver and an LED driver are needed for separately driving the fluorescent lamps that realize main lighting and the LEDs that realize weak lighting.
Circuits and methods for driving fluorescent lamps and LEDs have been developed.
For example, the patent EP2163139B2 in the title of “CIRCUIT ARRANGEMENT AND METHOD FOR OPERATING AT LEAST ONE LED AND AT LEAST ONE FLUORESCENT LAMP” discloses a circuit and method for driving at least one fluorescent lamp and at least one LED.
FIG. 1 schematically shows a structure of a circuit according to the above mentioned patent. Input terminals E1, E2 are coupled to a power supply AC voltage UN by means of a switch S. The input terminals E1, E2 are coupled to a main rectifier 12, the input terminal E1 is also coupled to a first input terminal of an auxiliary rectifier 14 via a capacitor CS1, and the second input terminal E2 is coupled to a second input terminal of the auxiliary rectifier 14 via a second capacitor CS2. The two input terminals of the auxiliary rectifier are directly coupled to an X capacitor CX1. An output end of an inverter is coupled to a fluorescent lamp LA, wherein the capacitor C5 is designed as a triggering capacitor. Moreover, the input terminals E1, E2 of the main rectifier 12 are coupled to an input end of a timer 20, a first output end of the timer 20 is coupled to a control electrode of an LED switch Q3, and a second output end thereof is coupled to a reference electrode of the LED switch Q3. As is depicted by dashes, a coupling of the timer 20 to the operating electrode of the LED switch Q3 can be provided. A starting capacitor C1 is coupled between the output ends A13 and A14 of the auxiliary rectifier 14, a voltage UC1 being stored in the starting capacitor. Coupled in parallel with the starting capacitor C1 is the series circuit formed by a plurality of LEDs (illustrated by the LEDs LD5 and LD6), and also the path operating electrode-reference electrode of the LED switch Q3. Moreover, the voltage UC1 is coupled to one terminal of the DIAC D14, the other terminal of which is coupled to a control electrode of a switch of the inverter 16. The midpoint of the inverter 16, which includes at least two switches (not illustrated), is coupled to the voltage UC1 via a pull-down circuit 22.
The circuit shown in FIG. 1 alternately drives the fluorescent lamp and the light-emitting diode by using two rectifiers (i.e., the main rectifier 12 and the auxiliary rectifier 14) under the control of the timer 20. Thus, the circuit is complicate.
Therefore, there is a need of a circuit and method capable of simply and conveniently driving a fluorescent lamp and a light-emitting diode.